ABSTRACT

The EPA approved federal reference methods (FRM) for measuring particulate matter concentrations of PM₁₀ and PM_2.5 are affected by the particle size distribution (PSD) of the particulate matter (PM) present in ambient air. The PSD of PM in the ambient air emitted by agricultural operations (rural areas) is significantly larger than that of PM present in urban areas. Typically, urban PM will have a mass median diameter (MMD) less than 10 μm aerodynamic equivalent diameter (AED) whereas, agricultural PM will have an MMD larger than 10 μm AED. An MMD of as high as 24 μm AED has been reported for PM emitted through agricultural operations. The EPA- approved FRM PM₁₀ and PM_2.5 samplers have been shown to exhibit over-sampling problems for particles having MMDs of greater than 10 μm such as agricultural dust. As a consequence, agricultural operations are not being regulated fairly. This work presents some procedures that can be done to correct this over sampling problem.